I am encountering the same error with my bot, based on Pywikibot...
I am still unable to fetch more than a few pages from Wikipedia. The requests are authenticated. The bot has been running for about 13 years but most of my tasks are now blocked...
I added a "user_agent_description" parameter in user-config.py (and also edited pywikibot/comms/http.py to add the "/1.0" string) to customize the user agent.
I currently used the following string:

@Aklapper I removed most of my project from the cluster several months ago and I host it on my own server ; I just host simple tasks on wmflabs for this project. Regards

@Smalyshev thanks again, it works fine!

@Smalyshev Thank you for this fix! Is there a way to know if/when this is deployed to query.wikidata.org? Regards

Hi Chicocvenancio ,